Method for removing weakly bound functional moieties from cell targeting conjugates

Abstract

This disclosure describes a method for preparing stable cell targeting conjugates. A further aspect of this disclosure relates to the stable cell targeting conjugates obtainable by the method and to pharmaceutical compositions comprising these stable cell targeting conjugates. A last aspect of this disclosure relates to the use of these conjugates and pharmaceutical compositions as a medicament.

The invention claimed is: 
     
       1. Stable cell targeting conjugates produced by a method comprising:
 treating a composition of cell targeting conjugates with thiourea such that weakly bound functional moieties are removed from the cell targeting conjugates so as to obtain a composition comprising stable cell targeting conjugates, 
 wherein the cell targeting conjugates comprise a targeting moiety and at least one functional moiety bound thereto via a linker comprising a transition metal complex, and 
 wherein the stable cell targeting conjugates have had weakly bound functional moieties removed therefrom as may be determined by storing a composition of the stable cell targeting conjugates in phosphate-buffered saline at room temperature for 48 hours, and afterwards, applying size exclusion chromatography to the composition, and wherein no significant amount of detached functional moiety or functional moiety-linker complex is observed in the composition in comparison to untreated conjugates. 
 
     
     
       2. Stable cell targeting conjugates produced by a method comprising:
 treating a composition of cell targeting conjugates with an agent that removes weakly bound functional moieties from the cell targeting conjugates so as to obtain a composition comprising stable cell targeting conjugates, 
 wherein the cell targeting conjugates comprise a targeting moiety and at least one functional moiety bound thereto via a linker comprising a transition metal complex, and 
 wherein the stable cell targeting conjugates have a serum stability that is at least two times greater than the serum stability of untreated conjugates. 
 
     
     
       3. The stable cell targeting conjugates of  claim 2 , wherein the linker comprises a platinum complex. 
     
     
       4. The stable cell targeting conjugates of  claim 2 , wherein the linker comprises a cis-platinum complex. 
     
     
       5. The stable cell targeting conjugates of  claim 2 , wherein the relative binding affinity of the agent for the linker is less than the relative binding affinity of the linker for histidine. 
     
     
       6. The stable cell targeting conjugates of  claim 2 , wherein the agent is a competitor S-donor compound. 
     
     
       7. The stable cell targeting conjugates of  claim 2 , wherein the agent comprises thiourea, sodium thiosulphate (STS), glutathione, cysteine, N-acetylcysteine, potassium thiocyanate, sodium thiocyanate, biotin, methionine, n-acetyl-methionine penicillamine, mesna, or combinations of any thereof. 
     
     
       8. The stable cell targeting conjugates of  claim 2 , wherein the targeting moiety is a peptide, an antibody, an antibody fragment or engineered variant thereof. 
     
     
       9. The stable cell targeting conjugates of  claim 2 , wherein the at least one functional moiety is a therapeutic compound, a diagnostic compound or a chelating agent. 
     
     
       10. A pharmaceutical composition comprising:
 the stable cell targeting conjugates according to  claim 1 ; and 
 a pharmaceutically acceptable carrier. 
 
     
     
       11. The stable cell targeting conjugates of  claim 3 , wherein the platinum complex is a cis-platinum complex comprising an inert bidentate moiety. 
     
     
       12. The stable cell targeting conjugates of  claim 1 , wherein the method comprises:
 treating the composition of cell targeting conjugates with thiourea for 10 to 240 minutes. 
 
     
     
       13. A pharmaceutical composition comprising:
 the stable cell targeting conjugates of  claim 2 ; and 
 a pharmaceutically acceptable carrier.